04' 450 starting trouble!

Last night I thought that I would go out into the garage and fire up the beast and let it breathe a little bit. But before I knew it my legs where beat from kicking it. So, my in my infinite wisdom decided to push start it. Still no go! It would fire for a second and then quit. It has been about a month since the bike was run and not sure if the plug was fouled or not. I went out about an hour after that and it took some kicking but the beast finally came to life. But boy did she run rough for a while. The temp. has dropped here about 30 degrees and wondering if that has something to do with my problems. Do I need to re-jet? Or does anyone know what the problem might be? The bike was bought brand new in May and has started the first kick every time except for last night. :cry:

Adjust your fuel screw out since the weather got colder. Needs more fuel since the air is more dense. Might need to rejet, but definitely the fuel screw first. Do you have an aftermarket fuel screw? If not, buy one. It just makes adjustment that much easier if you dont have to have a screwdriver. Were you using the choke and it was still having a hard time starting? BTW turn the fuel screw out in 1/8th-1/4 turn increments.

I don't have a fuel screw. I have thought about getting one but so far things have been great with it. Yes, the choke was on. I have read several bits in here that say to give the throttle two quick thrusts before a cold start and it will start alot easier. I did that last night and wondering if I flooded it or there is a bigger problem ahead! After I got it started it ran like @#$%$# for about 2 minutes. Then I rode it down the street and it worked itself out. Ran great after that. Hmmmmmmmm

I never give mine any throttle before she is running. I would always try first without it, if after a while nothing lit, I might try one twist. It always caused me problems before I did the BK mod. I have never needed it.


I had the same problem recently. I actually took the carb off and cleaned it with carb cleaner. Make sure to remove the jets, spray the carb with the cleaner and it should run perfectly.

Good luck!

I don't have a fuel screw.

Yes you do have one. :cry:

You just don't have the aftermarket, extended screw you are considering buying.

If you've never adjusted the fuel screw (referred as the pilot screw in the manual) you need to. Mine was only .5 turns when I got it and the bike would barely start and wouldn't idle. I put it to 2.5 turns out and it ran fine.

I got a zipty to make it easier to adjust because it made that big of a difference. Now I adjust it a little almost every ride. It was worth every penny. They're only like $20, go ahead and get one.

get a small regular screwdriver and adjust your fuel screw in the bottom of the float bowl. Lightly seat it, then back it out about 2.5 turns as a baseline.

If it helps a little, but not enough, consider the next size pilot jet up.

i have been having the same troubles. i adjusted my air screw but i need a bigger pilot i think a 45. mine starts a lot better if i twist the throttle twice, quickly, before any cold start. once its warmed up i dont do that and it fires right up. i have had mine idle and then die quickly after starting and i could kick the heck out of it for days and it wouldnt start until i put a new plug in it.

Some of the later bikes have needed a twist of the throttle to light them up according to some here. BTW there is no air screw on a YZF, it is a fuel screw.

Put in a 72 starter jet (choke circuit) in for the winter. I run a 68 in the summer. Huge difference much easier starting when cold!!!!!!!!! :cry:

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